Measurement of earth formation pressures



'aa a Jan. 21, 1969 P. A. PAYNE 3,422,672

MEASUREMENT OF EARTH FORMATION PRESSURES Filed Dec. 27, 1966 SheetINVENTOR. PERCY A. PAYNE,

AT TORNEY.

Jan. 21, 1969 P. A. PAYNE MEASUREMENT OF EARTH FO RMATIQN PRESSURESSheet Filed Dec.

ATTORNEY.

United States Patent 3,422,672 MEASUREMENT OF EARTH FORMATION PRESSURESPercy A. Payne, Tylertown, Miss., assignor to Esso Production ResearchCompany, a corporation of Delaware Filed Dec. 27, 1966, Ser. No. 604,854U.S. Cl. 73-151 Int. Cl. E21b 47/06 8 Claims ABSTRACT OF THE DISCLOSUREApparatus is incorporated in a drill bit that can be extended throughthe lower end of the bit to seal against the earth formation to isolatethe drill string bore from the annulus around the drill string. Channelsin the drill BACKGROUND OF THE INVENTION This invention is directed toapparatus for measurement of earth formation pressures, and moreparticularly to apparatus for inclusion as part of a drill stein formeasuring formation pressures at the bottom of a borehole.

During the course of drilling boreholes using the rotary drillingtechnique, often it is desirable to measure the pressure of a formationbeing penetrated by the drill string at its lowest end. To this end,usually it is necessary to pack of]? the lower end of the borehole, sothat a pressure measurement can be obtained which is not affected by theweight of the drilling fluid in the borehole above the level at whichthe pressure measurement is conducted. Such an operation usuallyinvolves pulling the conventional drill stem and running specialequipment into the borehole or using a special drill stem whereinexpandible packers are incorporated on the outer surface thereof. Forobvious reasons, it is desirable, if possible, to avoid the use ofpackers in connection with formation pressure measurements.

SUMMARY OF THE INVENTION In accordance with one aspect of the presentinvention, there is provided a drill string section having alongitudinal bore therein and an annular drill bit connected to thelower end of the drill string section. An annular cavity is provided inthe drill string section and the drill bit section that opens into theborehole at the lower end of the drill bit section. Formation sealingmeans is provided in the cavity which is adapted to move into the cavityfrom a normally retracted position, and is further adapted to extendfrom the lower end of the drill bit to contact the earth formation belowthe drill bit. The sealing means includes an actuating piston for movingthe sealing means downwardly under the impetus of hydraulic pressureexerted thereon. A passageway means in the drill string section providesfluid communication between the longitudinal bore and the upper end ofthe cavity. Within the drill string section there is provided a secondcavity for receiving a pressure recorder means, said cavity intersectsthe longitudinal bore at a position below the opening of the passagewayinto the bore. Annular valve means in the bore of the drill stringsection normally closes the openings of the second cavity and thepassageway into the bore and is movable under the impetus of hydraulicpressure exerted from the upper end of the drill string section to aposition whereat it opens the passageway and the second cavity intofluid communication with the drill string bore. The upper end of thevalve means BRIEF DESCRIPTION OF THE DRAWING Objects and features of theinvention not apparent from the above discussion will become evidentupon consideration of the following detailed description of theinvention taken in connection with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional view of a preferred embodiment of theinvention;

FIG. 2 is a view similar to FIG. 1 illustrating an actuated position ofthe apparatus;

FIG. 3 is a sectional view taken along section 33 of FIG. 1;

FIG. 4 is a cross section of the formation sealing apparatus illustratedin FIG. 1;

FIG. 5 is a sectional view taken along section 5-5 of FIG. 4;

FIG. 6 is a sectional view taken along section 6--6 of FIG. 4;

FIG. 7 is a view similar to FIG. 6 illustrating a modi fication of theinvention; and

FIG. 8 is a sectional view of a pressure recorder suitable for use withthe invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference now generally toFIGS. 1, 2, and 3, there is illustrated the lower end of a drill stringcomprising drill collar sections 1 and 5 and a drill bit 49. The drillbit 49 is here illustrated as being of the diamond type, being generallyannular in shape, and having a diamond studded matrix 53 on the outerand lower surfaces thereof. The drill collar sections 1 and 5 and thebit 49 are scrcw-threadedly connected together. A chamber 41 in thelower end of drill collar section 1 extends through the drill bit 49 andopens into the borehole at the lower face of the drill bit. A passageway11 interconnects the upper end of the chamber 41 and the bore of thedrill string section, the passageway terminating at the upper end in thebore of the drill collar 1 through passageway section 11A. Thepassageway 11 also communicates with the bore of the drill collar sub 1through a passageway section 23 which is controlled by a check valve 21that permits fluid flow only from the passageway into the bore of thedrill collar. Within the chamber 41 is positioned a ring-shaped piston43 adapted to reciprocally move in the chamber 41 and urged upwardlytherein by a plurality of coil springs 51 (see FIG. 4). The ring piston43 is connected to an annular formation sealing ring 47 by means of aplurality of connecting ribs 45. The formation sealing ring 47terminates at its lower end in substantially a knife edge so as to cutinto the formation immediately below the drill bit 49 responsive topressure thereon exerted through the ring piston 43 and connecting ribs45. A pair of O-rings and 56 provide a fluid seal between the ringpiston 43 and the drill collar sub 1, and a pair of O-Iings 57 and 58provide a seal between the drill bit 49 and the formation sealing ring47. The ring piston 43 may be formed of tool steel, and the sealing ring47 may be formed of tungsten carbide. The springs 51 are positionedbetween the lower end of the ring piston 43 and a shoulder in thechamber 41 so as to urge the ring piston 43 upwardly, as viewed. Thesealing ring 47 may be circular in cross section as illustrated in FIG.6, but is preferably oval in cross section, as illustrated at 47A inFIG. 7, so that a concentric core will not be cut during drillingoperations.

Within the drill collar sub 1 there is positioned an annular sleeve 9,the outer surface of which conforms to the inner surface of the drillcollar sub 1. An annular flange 31 at the bottom of the sleeve 9 bearsagainst a shoulder formed by a narrowing of the bore of the drill collarsub 1 to prevent further upward movement thereof. In this position, aport 25 in the sleeve 9 is aligned with the passageway section 23 topermit flow of liquid through check valve 21. An annular nut 39screwthreadedly engages the drill collar sub 1 within the bore of thedrill collar sub and provides a reaction member for a coiled spring 36that engages the sleeve 9 to urge the sleeve 9 upwardly. O-rings 17 and19 above the passageway section 11A provide a. fluid seal between thesleeve 9 and the drill collar sub 1.

A pressure relief cavity 27, which is most perspicuously illustrated inFIGS. 1, 2, and 3, is threadedly ported to the exterior of the drillcollar sub 1 so as to accommodate a differential pressure recorder 29:Effectively there is provided a passageway between the exterior and boneof the drill collar sub 1 that intersects the longitudinal bore of thesub 1 to accommodate the differential pressure recorder so as to measurethe differential pressure between the bore and a reference pressure,such as a pressure equal to atmospheric.

In FIG. 8 there is illustrated a suitable pressure recorder for use asrecorder 29. This recorder includes a housing member 71 sealed at oneend by a diaphragm 73 and at the other end by an end section 91. A wall85 acts as a journal and support for the shaft 84 of a revolving spool89 on which is mounted a pressure recorder chart. The other end of theshaft 84 is supported by the end section 91. A pivot rod 79 is pivotallysupported by a pivot member 77 between the diaphragm 73 and the wall 85.A rod 75 connects the pivot rod 79 to the diaphragm. A stylus linkagemember 81 is connected to the other end of the pivot rod 79 and supportsa stylus 86 which engages the chart on the spool 89. A release pin 83 isaffixed to the stylus linkage member and is inserted in a recess (notshown) in the spool 89. Responsive to differential pressure across thediaphragm 73, the diaphragm will move to the right as viewed, causingthe release pin 83 to be withdrawn from its slot in the spool 89, andallowing the spool to rotate. The stylus 86 engages the chart and movesto the left as viewed, thus providing an indication of the differentialpressure across the diaphragm 73. When the differential pressure acrossthe diaphragm 73 is reduced, the pin 83 will bear against the spool 89and will fall into the recess in the spool 89 to stop the spool. Anannular array of such slots can be provided so that the spool can beimmediately stopped in the event that it is desired to make a number ofpressure readings.

The operation of the apparatus described heretofore is as follows.During normal drilling operations the position of the components of theapparatus will be as illustrated in FIG. 1, with the piston 43 and theseal ring 47 retracted into the drill bit 49 and drill collar sub 1.When it is desired to perform, a pressure measurement, drillingoperations are stopped. A wire line go-devil or retrievable plug 3,having a fishing-head 7, a cap member 13 adapted to seat on the upperend of sleeve 9, and a body member adapted to be inserted into thissleeve 9, is lowered into the well and seated on the upper end of thesleeve 9. Hydraulic pressure is then exerted through the drill string onthe retrievable olug 3. The sleeve will be forced downwardly into theposition illustrated in FIG. 2.. The function of port 33 at the lowerend of sleeve 9 is to provide vacuum relief so that the sleeve canfreely move downwardly against the coiled spring 36. When port isaligned with cavity 27 hydraulic pressure will be exerted throughpassage .vay 11 onto the upper end of ring piston 43 to force the ringpiston and formation seal ring 47 downwardly, as illustrated in FIG. 2.The knife edge 4 lower end of the seal ring 47 will be forced into theformation immediately below the drill bit 49 so as to isolate the boreof the drill bit and the portion of the longitudinal bore of the drillcollar sub 1 below plug3 from the borehole annulus and from the portionof the drill string bore above plug 3. The pressure of formation fluidsthus will be exerted upwardly through the bore of the drill bit 49 andthe drill collar sub 1 and through the port 25 against the diaphragm ofthe formation pressure recorder 29. As soon as the pressure recordinghas been made, the hydraulic pressure can be released so that the sleeve9 will be forced upwardly again to the position illustrated in FIG. 1.Springs 51 will force the ring piston 43 upwardly and fluids in thepassageway 11 will be forced through the check valve 21 into the bore ofdrill collar sub 1. Drilling operations may be resumed, and if desired,another formation pressure measurement may be made at a later time. Whena round trip is made for the purpose of replacing the drill bit, or forother purposes, the formation pressure recorder can be removed and thechart recovered therefrom, and either the same recorder with anotherchart or a different recorder can be placed into the drill collar sub 1for future measurements.

Having described the principle of the invention and the best mode inwhich I have contemplated applying that principle, I wish it to beunderstood that the apparatus described is illustrative only, and thatother means can be employed without departing from the true scope of theinvention defined in the following claims.

What is claimed is: 1. Apparatus for measuring bottom hole pressure in aborehole, comprising: an annular drill string section; a bit subconnected to the lower end of said drill 7,string section; sealing ringmeans in said bit sub extendible from the lower end of said bit sub tocontact the lower end of said borehole responsive to hydraulic pressureexerted thereon; a channel in said drill string section from the bore ofthe drill string section to said sealing means; a pressure recorderopening to the interior of said drill string section; and meansincluding valve means in said drill string section movable underhydraulic pressure from a first to a second position thereof, normallyisolating the bore of said drill string section from said channel andfrom said recorder in said first position thereof, and in said secondposition thereof, permitting fluid communication between said channeland the upper end of said drill string section and between said pressurerecorder and the lower end of said drill string section, said valvemeans being adapted to receive a removable plug to permit hydraulicpressure to be exerted thereon. 2. Apparatus for measuring bottom holepressure in a borehole, comprising:

a drill string section having a longitudinal bore therein; an annulardrill bit section connected to the normally lower end of said drillstring section; an annular cavity in said drill string section and saiddrill bit section opening at the lower end of said drill bit section tothe borehole; formation sealing means in said cavity normally retractedinto said cavity and adapted to extend from the lower end of said drillbit to contact the earth formation below said drill bit, said sealingmeans including an extracting piston for moving said sealing meansdownwardly under the impetus of hydraulic pressure exerted thereon;passageway means in said drill string section opening into saidlongitudinal bore and into said cavity; pressure recording means; asecond cavity in said drill string section for receiving said pressurerecording means, said second cavity opening into said bore at a positionbelow the opening of said passageway means into said bore;

an annular valve means insaid bore of said drill string section normallyclosing the opening of said second cavity and said passageway means intosaid bore, movable under the impetus of hydraulic pressure exerted fromthe upper end of said drill string section to a position whereat itopens said passageway means and said second cavity into fluidcommunication with said bore at the upper end of said valve means beingadapted to receive a removable plug.

3. The apparatus of claim 2 wherein said annular valve means includes anannular sleeve in sliding contact with the interior of said drill stringsection, and port means in said sleeve means including spring meansbiasing said sleeve means to a position whereat said port means isisolated from said second cavity and whereat said sleeve means closesthe openings of said second cavity and said passageway into said bore.

4. The apparatus of claim 3 wherein second passageway means includingcheck valve means permits one-way fluid flow from said first passagewaymeans to said bore at a position through said port means in said sleevewhen said sleeve is in its normal position.

5. The apparatus of claim 3 further including an annular spring seat forsupporting said coil spring.

6. The apparatus of claim 2 wherein at least the lower portion of saidannular cavity is elliptical in cross section and the portion of saidformation sealing means in said lower portion of said annular cavity iselliptical in cross section.

5 7. The apparatus of claim 2 wherein the lower end of said formationsealing means is tapered to knife edge to facilitate penetration of theearth.

8. The apparatus of claim 2 wherein said formation sealing meanscomprises:

10 an annular sealing member;

an annular piston member; a plurality of ribs connecting said sealingmember and said piston member; and a plurality of coil springs betweensaid ribs for engaging said bit and said piston upwardly to bias saidpiston.

References Cited UNITED STATES PATENTS 2,497,185 2/1950 Reistle 175-2332,740,477 4/1956 Monaghan 175-233X RICHARD Ct QUEISSER, PrimaryExaminer.

JERRY W. MYRACLE, Assistant Examiner.

U.S. Cl. X.Rn

